Generally, a bend model or a three-dimensional solid model of, for example, a sheet metal product is provided with working attribute information which is electronic data representing only part of written information on design drawings of the sheet metal product prepared at a purchaser.
Namely, the working attribute information to be provided is standard attribute data such as data for dividing a model into component models and bend line data for unfolding bend positions of a bend model.
Working attribute information for preparing NC data for NC-machining a sheet metal product is added to, for example, an unfolded form of a component model.
On the other hand, an outsourcing center partly takes over the manufacturing of a sheet metal product for an order receiver according to a request from the order receiver. The outsourcing center also takes over computer operation (for example, CAD/CAM operation) for the order receiver. Working know-how (for example, tips for special working) obtained from the work relegated to the outsourcing center is only verbally informed to persons concerned.
Such a conventional working attribute information linking method has problems mentioned below.
Namely, design drawings transmitted from a purchaser to an order receiver describe every piece of information necessary for manufacturing a sheet metal product, and therefore, all of such information pieces are required to be added as working attribute information to a bend model.
However, if the bend model and working attribute information employ different file formats, a bend model interface (for example, an interface program for reading bend model data for CAD/CAM software) of existing application software (for example, CAD/CAM software to handle bend models) must be corrected. This requires the updating of applications already supplied to vendors and increases the number of man-hours.
Another problem is that only adding partial information to a bend model hinders digitization of working know-how and prevents proper transfer of information.
For sheet metal component designing, computer aided design (CAD) has been employed to allow designers interactive designing with computers. The CAD employs, for example, object-oriented sheet metal models for the convenience of metal sheet component designing.
Designing sheet metal components involves the editing of butting parts of a sheet metal model. More precisely, it is necessary to edit a connection where nonparallel two sheet-metal faces butt against each other (butting) and a connection where parallel two sheet-metal faces lap over each other (lapping).
FIGS. 1A to 1E are views explaining concrete examples of editing a butting part on a conventional sheet metal model.
A sheet metal component having an unfolded view of FIG. 1A and a solid view of FIG. 1C is considered.
The sheet metal component has an apex “a” as shown in the solid view, and around the apex, involves a both-side-contracted butting part as shown in an enlarged partial view of FIG. 1B. In the FIGs., a dotted line represents a bend line, and the same is applicable to the following description.
After the editing of the sheet metal model, a sheet thickness or a welding method may be changed to raise a necessity of changing the butting part.
In an enlarged partial view of FIG. 1E, the butting part is changed to one-side-contracted butting. To achieve this, CAD must be employed to again edit the shape of sheet metal as shown in an unfolded view of FIG. 1D. This is because CAD stores only a final shape of sheet metal.
Arrow marks in FIGS. 1D and 1E indicate directions in which the sheet metal is extended from the one-side-contracted state serving as a reference to the both-side-contracted state.
According to the conventional sheet metal model, changing a butting part due to a change in sheet thickness or welding method after the editing of the model requires a repetition of the editing of the sheet metal model.
FIGS. 2A to 2F are views explaining concrete examples of editing to be carried out when a sheet thickness is changed on a conventional sheet metal model.
A sheet metal component shown in an unfolded view of FIG. 2A and an enlarged partial view of FIG. 2B corresponds to the sheet metal component changed to one-side-contracted butting in FIGS. 1A to 1E. Namely, FIG. 2A corresponds to FIG. 1D and FIG. 2B to FIG. 1E.
If the thickness of the sheet metal is increased under this state, areas “b” shown in an unfolded view of FIG. 2C and an enlarged partial view of FIG. 2D cause interference at the one-side-contracted butting. Namely, if sheet thickness is increased without changing the shapes shown in FIGS. 2A and 2B, two parts of the sheet metal simultaneously occupy the same area at “b” to collapse the sheet metal model.
To solve the interference, the sheet metal model must be edited again. Namely, the shape of the sheet metal must be changed as shown in an unfolded view of FIG. 2E to avoid the interference. This realizes a one-side-contracted butting part containing the sheet thickness change as shown in an enlarged partial view of FIG. 2F.
As mentioned above, the conventional sheet metal model needs, if a sheet thickness is changed after the completion of the sheet metal model, a repetition of the editing of the sheet metal model to control connection parts. This increases the labor of an operator who edits the model as well as a risk of erroneous changes during the editing.